How do I build a still air box?

Take a clear plastic storage tote, lay it on its long side, and cut two arm holes on the front spaced about a shoulder-width apart. Some builders angle the holes downward for comfort. Wipe the inside with 70% isopropyl before each session, place your sterilised jars and tools inside, and work slowly so the air stays still. It is a cheap, effective first upgrade to sterile work.